Lessons from a mouse model characterizing features of vascular cognitive impairment with white matter changes

Animal models of vascular dementia: translational potential at the present time and in 2050

ABSTRACT: Vascular dementia is a heterogeneous syndrome, and includes subcortical ischemic vascular dementia. For translational research, subcortical ischemic vascular dementia is an appropriate target since this is the most prevalent subtype and exhibits relatively uniform clinical and neuropathological changes. These changes consist of hypertensive arteriolar changes, lacunar infarctions, hypertensive hemorrhage and white matter lesions. Among various species, rodents are most frequently used, but their small volume of white matter may impede analysis of white matter lesions. Primate models have a larger volume, but the degree of white matter lesions is inconsistent. Animal models should accommodate the effect of aging and comorbidities, and in the case of primate models, low accessibility should be overcome by repeated and quantitative examinations using modern neuroimaging techniques and functional measures, especially for memory and motor function. There is no model that replicates all features of subcortical ischemic vascular dementia and, therefore, rodent and primate models should be selected appropriately for translational research.

A mouse model of chronic cerebral hypoperfusion characterizing features of vascular cognitive impairment

Vascular dementia or vascular cognitive impairment occurs as a result of persistently compromised blood flow to the brain and represents the second most common type of dementia after Alzheimer's disease. In order to investigate its underlying mechanisms, a mouse model of chronic cerebral hypoperfusion has been developed, which involves the narrowing of the bilateral common carotid arteries with newly designed microcoils. This mouse model provides a unique platform to investigate the mechanisms of angiogenesis following chronic cerebral hypoperfusion and to explore potential drugs or cell therapies designed to enhance angiogenesis as a preclinical step toward developing novel treatments for dementia of vascular origin.

Mechanisms of oligodendrocyte regeneration from ventricular-subventricular zone-derived progenitor cells in white matter diseases

White matter dysfunction is an important part of many CNS disorders including multiple sclerosis (MS) and vascular dementia. Within injured areas, myelin loss and oligodendrocyte death may trigger endogenous attempts at regeneration. However, during disease progression, remyelination failure may eventually occur due to impaired survival/proliferation, migration/recruitment, and differentiation of oligodendrocyte precursor cells (OPCs). The ventricular-subventricular zone (V-SVZ) and the subgranular zone (SGZ) are the main sources of neural stem/progenitor cells (NSPCs), which can give rise to neurons as well as OPCs. Under normal conditions in the adult brain, the V-SVZ progenitors generate a large number of neurons with a small number of oligodendrocyte lineage cells. However, after demyelination, the fate of V-SVZ-derived progenitor cells shifts from neurons to OPCs, and these newly generated OPCs migrate to the demyelinating lesions to ease white matter damage. In this mini-review, we will summarize the recent studies on extrinsic (e.g., vasculature, extracellular matrix (ECM), cerebrospinal fluid (CSF)) and intrinsic (e.g., transcription factors, epigenetic modifiers) factors, which mediate oligodendrocyte generation from the V-SVZ progenitor cells. A deeper understanding of the mechanisms that regulate the fate of V-SVZ progenitor cells may lead to new therapeutic approaches for ameliorating white matter dysfunction and damage in CNS disorders.

The pathobiology of vascular dementia

Vascular cognitive impairment defines alterations in cognition, ranging from subtle deficits to full-blown dementia, attributable to cerebrovascular causes. Often coexisting with Alzheimer's disease, mixed vascular and neurodegenerative dementia has emerged as the leading cause of age-related cognitive impairment. Central to the disease mechanism is the crucial role that cerebral blood vessels play in brain health, not only for the delivery of oxygen and nutrients, but also for the trophic signaling that inextricably links the well-being of neurons and glia to that of cerebrovascular cells. This review will examine how vascular damage disrupts these vital homeostatic interactions, focusing on the hemispheric white matter, a region at heightened risk for vascular damage, and on the interplay between vascular factors and Alzheimer's disease. Finally, preventative and therapeutic prospects will be examined, highlighting the importance of midlife vascular risk factor control in the prevention of late-life dementia.

The persistent effects of maternal infection on the offspring's cognitive performance and rates of hippocampal neurogenesis

Accumulating evidence indicates that perinatal infection is a major cause of neonatal neurologic morbidity. Here we explored the effects of maternal infection on the offspring's cognitive performance and hippocampal neurogenesis. Pregnant rats were treated with Escherichia coli suspension and allowed to deliver. Proliferating cells in the hippocampus were examined at postnatal (P) 3, 7, 14, and 28 days and neuronal survival/differentiation was assessed at P28. Additionally, we examined the expressions of BDNF, TrkB and Akt. The cognitive performance of the offspring was assessed by the Morris water maze test. We found that maternal infection significantly impaired the offspring's spatial learning ability and spatial memory, thus could delay the cognitive performance development. Maternal infection significantly increased the number of proliferating cells in the offspring's hippocampus at postnatal 3, 7 and 14 days, accompanied by significantly increased expressions of BDNF, TrkB and p-Akt at postnatal 3 and 7 days. On postnatal 28 days, maternal infection did not significantly affect the neuronal and glial differentiation, nor any significant changes in the expression levels of BDNF and TrkB in the hippocampus. Our result suggests that the hippocampal neurogenesis level may increase during early postnatal period after maternal infection. Increase of BDNF/TrkB expression and Akt activity may be the contributing molecular mechanism.